Travelers can leave their cars at the arrival level of the ParkingPLUS structure. As they leave, they confirm on a touch-screen that no one is in the car. The robot valet, nicknamed "Ray," takes it from there.

The robot measures the vehicle, picks it up with a forklift-like system, and takes it to the back area, where it will position it in one of the 249 parking spots reserved for automated valets. The machine is capable of carrying standard cars weighing up to 3.31 tons.

The robot valet is even connected to the airport's flight data system, and by checking customer trip data with the database, Ray knows when the customer will return for the vehicle. A traveler can note any itinerary changes in a parking app, which is available for iOS and Android.

Düsseldorf's airport is relatively small, and officials touted the convenience of heading to the terminal from the parking structure entrance. Ray "makes the distances between planes and passengers' vehicles even shorter," according to a statement from the airport.

"Our product is especially appealing to business travelers, who arrive at the airport shortly before the flight, seek efficient parking, and return within a few days," said Thomas Schnalke, the airport's managing director.

The introductory rate for robot valet parking at Düsseldorf is 29 euros ($39.59) per day or 4 euros ($5.46) per hour. Although the airport is targeting business travelers in a hurry, the service is open to anyone.

If airport customers use the robot valet, airport officials said they would consider expanding the system.